Jet centrifuge

ABSTRACT

A high speed bowl centrifuge of the type having a rotatably mounted bowl and an independently, rotatably mounted central support member which is enclosed thereby upon which a plurality of disks are coaxially mounted for rotation therewith. The periphery of the disks and the inner surface of the bowl define therebetween a substantially annular space, into which, in the preferred embodiment, at least one pitched extension protrudes from at least one disk. Under normal centrifuging operations, the central support member and bowl are rotated in a common direction at a common rotational speed and thus sludge builds up at the inner surface of said bowl. During the cleaning operation the central support member is rotated in such a direction as to urge sludge towards said sludge outlet due to the pitch of said extension. The bowl may also be rotated in the opposite direction as to apply a stripping force to the sludge. Furthermore, both of the above-mentioned rotations are at a substantially lower rotational speed than the centrifuging speed so that the extension encounters less compacted sludge.

United States Patent 91 Weiland 1 JET CENTRIFUGE [76] Inventor: Carl W. Weiland, 2980 lnterlaken,

Orchard Lake, Mich. 48033 22 Filed: July 16,1971

21 Appl.No.: 163,469

[52] US. Cl 233/38, 233/7, 233/19 R, 233/23 R [51] Int. Cl B04b 1/00 [58] Field of Search 233/7, 19 R, 20 R, 233/29, 30, 35, 36, 39, 23 R, 38, 3

[56] References Cited UNITED STATES PATENTS 2,622,794 .12/1952 Smith... 233/7 3,126,337 3/1964 Smith 4 233/21 X 3,494,542 2/1970 Craig et a1. 233/7 3,282,497 11/1966 SchmiedeL. 233/7 1,435,545 11/1922 Morris 233/7 FORElGN PATENTS QR APPLICATIONS 456,353 11/1936 Great Britain....; 233/7 4/1932 Germany 2313/? 1 ,lune 26, 1973 Primary Examiner-George H. Krizmanich Atrbrney-Cushman, Darby & Cushman [57] ABSTRACT A high speed bowl centrifuge of the type having a rotatably mounted bowl and an independently, rotatably mounted central support member which is enclosed thereby upon which a plurality of disks are coaxially mounted for rotation therewith. The periphery of the disks and the inner surface of the bowl define therebetween a substantially annular space, into which, in the preferred embodiment, at least one pitched extension protrudes from at least one disk. Under normal centrifuging operations, the central support member and bowl are rotated in a common direction at a common rotational speed and thus sludge builds up at the inner surface of said bowl. During the cleaning operation the central support member. is rotated in such a direction as to urge sludge towards said sludge outlet due to the pitch of said extension. The bowl may also be rotated in the opposite direction as to apply a stripping force to the sludge. Furthermore, both of the abovementioned rotations are at a substantially lower rotational speed than the centrifuging speed so that the extension encounters less compacted sludge.

1 Claim, 3 Drawing Figures JET CENTRIFUGE BACKGROUND OF THE INVENTION More particularly, this invention pertains to devices associated with the disk assembly of a bowl centrifuge for urging sludge towards a sludge opening.

2. Description of the Prior Art Bowl centrifuges are commonly provided with a plurality of disks separated by spacing plates and rigidly mounted to a rotatably mounted central support member. The disk assembly is also commonly enclosed by a closed bowl or outer jacket to form therewith an annular space. Finally, it is also well known to provide a converging spiral mounted to a perforated drum, or the like, which encloses the disk assembly and urges sludge, which has collected in the annular space due to the centrifugal force created by the centrifuge, towards a sludge outlet.

There are two major problems with this type sludge removal system. First, the perforated drum or the like collects a quantity of sludge due to its positioning at the outer periphery of the disk assembly. Secondly, since the spirals are not integral with the disks, the great centrifugalforces which act in the annularspace when the central support member undergoes rapid rotation cannot be efficiently counteracted. Thus, either the centrifuge must be operated at a lower speed, or the connections between the spirals and their mounting means will be subjected to a tearing stress. 7

Furthermore, this tearing effect is aggravated in known centrifuges wherein the sludge removal takes place at normal operating speeds because the sludge becomes caked at higher speeds and the spirals are bent in pushing against the sludge.

The U.S. Pat. to Hiller, No. 3,275,230, issued Sept. 27, 1966, partially overcomes the first of the abovementioned difficulties but not the latter one.

In Hiller, the perforated drum is dispensed with and, instead, as shown in FIGS. 3 and 4, the spiral segments are supported by extensions from spacing plates which separate the disks of the disk assembly. Furthermore, in the embodiment shown in FIGS. 1 and 2 of Hiller the extensions from the spacing plates form an interrupted spiral and no spiral segments are used.

While the above Hiller embodiments overcome the problem of sludge buildup on the spiral mounting means, such as perforated drums, they are still subject to the other problem discussed above, namely the problem of tearing stress, since the spiral support means or extensions are removably secured to the-disks through therelatively small and thin spacing plates, in each embodiment of Hiller. These points of attachment to the disks form points of attack when the spiral means is subjected to strong centrifugal forces.

In'addition, since the outer jacket of Hiller is rotated at its normal speed during the scraping operations, the sludge deposited thereupon is tightly compacted by the centrifugal forces and this causes bending stress against the spiral means. Finally, since the Hiller spiral means is continually rotated relative to the outer jacket (as is also the case in the other prior art systems) there is continual wear as the spiral means engages the tightly compacted sludge.

SUMMARY OF THE INVENTION It is the object of this invention to provide a sludge removal system associated with a disk assembly which is free from the disadvantages of the prior art discussed above. More specifically, it is one object of the invention to provide a scraper means which is integral with the disks which can efficiently transfer the centrifugal forces acting upon the scraper means to the central support means to thus allow very high centrifuging speeds without the danger of the scraper means separating from the disk assembly.

It is another object of the invention to provide a sludge removal scraper means which removes sludge at a low rotational speed which thus exposes the scraper means to less compacted sludge.

It is yet another object of the invention to provide a sludge removal scraper means which does not move relative to the outer jacket during the centrifuging operation to thus avoid a constant wear upon said scraper means. I

The above, and other objects, are accomplished by the applicants high speed bowl centrifuge in which a first support means rotatably supports an outer jacket or bowl and a first power means rotates the outer jacket about its longitudinal axis while a second support means rotatably supports a disk assembly comprised of plural disks coaxially disposed within and completely enclosed by saidouter jacket. At least one of the disks has at least one integral,-pitched extension which extends into the annular area defined by the disks peripheries and the inner surface of the outer jacket. Since the extension is integral with the disk the centrifugal forces acting thereupon find no easily attachable point of discontinuity but, onthe contrary, are efficiently transferred to the central support means.

During the centrifuging operation, the central support member and outer jacket move in a common direction at a common high rotational speed and thus there is no relative movement between the extension andthe jacket to cause wear on the extension. Further, when it is desired to remove sludge from the centrifuge, the rotational speedof both the outer jacket and the central support member are reduced and then their relative directions of rotation are reversed. The extension or extensions are so pitched that their direction of rotation of the central support during the sludge removal step urges the sludge towards the sludge outlet.

Since the sludge removal takes place at comparatively low rotational speeds the extensions do not encounter tightly caked sludge. Furthermore, the different directions of rotation of the central support member and outer jacket during the cleaning operation create eddy' currents in the annular space which help to strip sludge from the inner surface of the outer jacket which enhances the sludge removal action.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a center line sectional side view of a bowl centrifuge in accordance with the invention;

FIG. 2 is a front view of a disk having extensions in accordance with the invention; and

FIG. 3 is a side view of the disk shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the invention will now be described with regard to the drawings in which the same elements are indicated by the same reference numerals throughout.

In FIG. 1, it is seen that liquid containing sludge or the like enters the centrifuge bowl by means of an inlet pipe 12 which is coaxially disposed with respect to the outer jacket.

The contaminated liquid then encounters and is deflected by the vanes 14 and the impeller 16, which are fastened to the central support shaft 28 by nut 58 and thus are rotating with shaft 28 in the range of 4,000 to 5,000 rpm with respect to the inlet pipe 12, into the annular region 18 which is defined between the circumference of the cylindrical disk assembly 20 and the cylindrical inner surface 22 of the bowl 10.

In this region the sludge contained in the contaminated liquid is forced outwards towards the inner surface 22 while the less dense pure liquid is drawn between disks 24 into the annular space 26 defined between the inner edges of disks 24 and the central support shaft 28.

The pure liquid then exits from the annular space 26 through apertures 30a and 30b in the rear disk assembly support 32. The apertures 30a and 30b, in turn, communicate with the annular compartment 34 via channels 36a and 36b which have been formed in the bowl support member 38. Finally, the pure liquid exits from compartment 34 via clear liquid outlet 35.

The disk assembly 20 is comprised of a plurality of disks 24 which are identical in construction to the disk shown in FIGS. 2 and 3 except that at least one of the disks has the integral extensions 40a and 40b which are shown in FIGS. 2 and 3. Thus each disk 24 has a generally disk-like configuration in which a larger circular aperture 42 tapers to form a frusto-conical annulus having a radially inwardly extending integral flange defining aperture 44 and a radially outwardly extending integral flange 46 surrounding aperture 42. Each disk 24 also has four rectangular spacer pieces 48 attached thereto on a single face thereof which are disposed at 90 with respect to one anothers longitudinal axes. Furthermore, the longitudinal axes of these spacer pieces are each bisected by a circle concentric with apertures 42 and 44, i.e., they are located at a uniform radial distance from the longitudinal axis. Thus, the spacer pieces 48 act to separate each disk from its neighboring disks when said disks are assembled into disk assembly 20 without overly disrupting liquid flow between the disks. It is also noted from FIG. 3 that the extensions 40a and 40b are disposed at the angle of incidence with respect to flange 46 but that extension 400 is disposed at an angle of 180 2a from extension 40b. In other words, the extensions 40a and 40b are pitched as in a propeller blade.

The disks 24 as described above are rigidly supported by shaft 28 by means of the rear disk assembly support 32, and the front disk assembly support 50 which is formed on the back of impeller 16. In other words forces applied to the tips of the disks are directly transferred to said shaft. The front disk support 50 also includes spacers 52 which are identical in construction, location, and operation to spacers 48. The rear disk assembly support 32 is keyed to shaft 28 while the impeller l6 and front disk assembly support 50 are fastened thereto by means of spindle 54 which protrudes through the axial aperture 56 in impeller 16. The free end of spindle 54 is threaded and nut 58 is screwed thereupon to complete the disk assembly 20 as well as to fixedly support vanes 14.

It is noted that in FIG. 1 only those disks 24 having extensions are shown in full section while the other disks are indicated schematically.

The central shaft 28 and thus the disk assembly 20 are rotatably mounted by ball bearings 62 and 64 and powered through pulley 66 which is keyed to said shaft 28, and endless belts 68 by a motor (not shown).

Similarly, the bowl support member 38 (and thus the bowl 10) are rotatably mounted by means of the tubular shaft 72 which forms an extension of support 38.

The shaft 72 which coaxially surrounds shaft 28 is supported by ball bearings 74 and 76 and is powered through the pulley 78 which is keyed thereto and endless belts 80 by a second motor (also not shown).

The entire centrifuge is supported by frame 84 in a known manner.

In the centrifuging mode of operation the two shafts 28 and 72 rotate in a common direction with a common rotational speed in the range of about 4,000 to 5,000 rpm,

Thus, in this mode, sludge is driven against the inner surface 22 of bowl 10 where it is tightly compacted by centrifugal force. However, since there is substantially no relative movement between the inner surface 22 and the extensions 40a and 40b, these extensions are not subjected to continuous wear during normal, centrifuging operations. Furthermore, these extensions are not subjected to great bending stress by pushing against tightly compacted sludge. Further, since the centrifugal forces to which the extensions 40a and 40b are subjected are transferred by the integral disk 24 to disk assembly 20 and thus shaft 28, there is no danger of shear at a point of attachment as in the prior art.

When it is desired to remove sludge from the annular space 18 the motor driving shaft 72 is controlled to slow the rotational speed of shaft 72 to a slower speed in the range of about 0-250 rpm, while the motor driving shaft 28 is first slowed and then reversed in direction so that shaft 28 now rotates opposite to shaft 72 with a speed of about 250 rpm.

The counter rotation produced in the annular space 18 by the counter rotation of the shafts 28 and 72 helps to loosen the sludge from said inner surface 22. Also,

the extensions 40a and 40b are so pitched that they drive the sludge towards tapered end of the bowl 10 where vanes 14 which are pitched in a manner identical to extensions 40a and 40b force the sludge through sludge outlet 84.

Once the annular space 18 is freed from sludge, the above described centrifuging mode may be resumed.

While the above description fully covers the preferred embodiment of the invention, many modifications are possible within its scope.

Thus, for example, the number of extensions supported on a given disk and the number of disks having extensions will vary with the amount and density of sludge which must be removed and, similarly the materials of construction of the disks and heat treatment etc. thereof may be varied to meet process requirements.

Similarly, the sludge buildup may be electronically or otherwise monitored as by sensor 100 and the motors driving shafts 28 and 72 automatically shifted between modes of operation as by control circuit 102.

In addition, only a single motor is required to operate both shafts if appropriate gearing is interposed between that motor and the shafts.

Finally, it makes no difference whether the rotation of the disk assembly 20 or the outer jacket is reversed so long as when the centrifuge operates in the cleaning mode, the sludge is driven by the pitch of extensions toward the sludge outlet.

What is claimed is:

l. In a high speed bowl centrifuge including a bowl having a central longitudinal axis, a first support means for rotatably mounting said bowl, a first power means for rotating said bowl about its longitudinal axis, a central support member coaxially disposed within and completely enclosed by said bowl, a second support means for rotatably mounting said central support v member independent from'said bowl, a second power means for rotating said central support member, and a set of disks, rigidly and coaxialiy mounted upon said central supporting member so as to define an annular space between the periphery of said disks and the inner surface of said bowl, and a sludge outlet from said bowl, the improvement comprising thatat least one of said disks includes at least one radial extension which extends into said annular space and is pitched to urge sludge therein toward said outlet on relative rotation between said bowl and said one disk, that at least one of said first and second power means is capable of various speeds of rotation, and including means for changing the mode of operation of said one power means so that, in the centrifuging mode, said bowl and said central support member may be rotated at a common rotational speed but, in the cleaning mode, said bowl and said central support member may be operated at different rotational speeds so that said extension urges sludge towards said sludge outlet, said changing means comprising a sludge sensor for measuring sludge buildup on the inner surface of said bowl and a control circuit connected to said sensor for controllingthe operation of said one power means. 

1. In a high speed bowl centrifuge including a bowl having a central longitudinal axis, a first support means for rotatably mounting said bowl, a first power means for rotating said bowl about its longitudinal axis, a central support member coaxially disposed within and completely enclosed by said bowl, a second support means for rotatably mounting said central support member independent from said bowl, a second power means for rotating said central support member, and a set of disks, rigidly and coaxially mounted upon said central supporting member so as to define an annular space between the periphery of said disks and the inner surface of said bowl, and a sludge outlet from said bowl, the improvement comprising that at least one of said disks includes at least one radial extension which extends into said annular space and is pitched to urge sludge therein toward said outlet on relative rotation between said bowl and said one disk, that at least one of said first and second power means is capable of various speeds of rotation, and including means for changing the mode of operation of said one power means so that, in the centrifuging mode, said bowl and said central support member may be rotated at a common rotational speed but, in the cleaning mode, said bowl and said central support member may be operated at different rotational speeds so that said extension urges sludge towards said sludge outlet, said changing means comprising a sludge sensor for measuring sludge buildup on the inner surface of said bowl and a control circuit connected to said sensor for controlling the operation of said one power means. 